CLOVERS AND OTHER LEGUMES 



241 



181. How Roots of Legumes open the SoU. — It is a 



well established fact that legumes almost invariably 

 leave fields in better condition than they find them. This 

 is unquestionably due in part to their deep rooting habit. 

 Red clover roots may penetrate the soil to a depth of 

 several feet while alfalfa roots have been found thirty 

 feet below the surface 

 of the ground. 



When these roots 

 decay, the soil is opened 

 to the passage of both 

 air and water, while 

 the humus made by 

 the decaying roots is 

 a valuable addition to 

 the soil. 



182. How Legumes 

 add Humus to the 

 Soil. — The roots of 

 legumes are not the 

 only valuable part of 

 these plants. Clovers, 

 cowpeas, or other leg- 

 umes may be plowed under, or they may be fed to 

 animals and the manure returned to the land with the 

 result in either case that the store of humus in the soil is 

 largely increased. 



183. How Legumes make other Plant Food Available. 



— It is apparent that the long roots of the legumes must 

 bring up plant food from considerable depths, and that 

 when thej' decay, this wall be hberated and thus become 

 available to the shallow-rooted cereals. Aside from this, 

 however, the decay of the humus, which these plants 



Fig. 104. 



Courlc^U Iowa State College. 



— Roots of young alfalfa extend 

 deep into the soil. 



